Ras and Ras-related (Rabs) proteins have been shown to play critical roles in human oncogeneis, controlling normal cell proliferation, inducing differentiated phenotypes and regulating membrane traffic. Over the past few years it has become apparent that many types of signals arriving at the cell surface activate Ras, and that active Ras and Rabs can stimulate multiple downstream targets. The major goal of future research will be to understand how Ras uses these multiple signaling cascades to mediate such diverse effects in cells. Rho family GTPases have also been shown to activate multiple downstream targets that ultimately lead to alterations in the actin cytoskeleton and gene transcription. Activation of Rho family members has also been shown recently to be an important component of Ras mediated cell transformation. Future goals in this area include elucidating the molecular details of how Rho proteins carry out their functions through multiple effector proteins, and how Rho family proteins are activated by upstream signals.